The present disclosure relates to an image reading apparatus and an image forming apparatus.
The following disclosure is known in relation to an image reading apparatus which reads in an image from an original document and outputs image data in accordance with the image. In a disclosure of this kind, the image reading apparatus includes a platen glass, a first carriage and a second carriage. An original document is placed on an upper surface of the platen glass. The first carriage includes a light source which irradiates light onto the original document placed on the platen glass and a first mirror which reflects image light reflected by the original document. The second carriage includes a second mirror which reflects light reflected from the first mirror, and a third mirror which further reflects the light reflected from the second mirror. The first carriage and the second carriage are movable in a sub-scanning direction which is perpendicular to a main scanning direction, which is a scanning direction of the image light.
A pair of wires for moving the first and second carriages in the sub-scanning direction are installed about the respective end sections of the first and second carriages in the main scanning direction. Pulleys around which the wires are wound are arranged on the first and second carriages.
In a disclosure such as that described above, if the positions of the pair of pulleys deviate in the sub-scanning direction, then the lengths of the pair of wires which move the carriages are not equal between the respective ends. Therefore, the mirror which is arranged on the carriage is arranged in an inclined fashion with respect to the main scanning direction. As a result of this, skewing and magnification problems occur in the read image. Therefore, in the prior art disclosure described above, a supporting member which movably supports the pulley with respect to the carriage is provided. By moving this supporting member with respect to the carriage, the position of the pulley is adjusted in the sub-scanning direction and the length of the wire is adjusted.
However, the wires are tensioned around the pulleys in two mutually opposing directions in the sub-scanning direction. The wires tensioned in these two directions are respectively wound around the outer circumferences of pulleys at a prescribed interval apart in the axial direction of the pulleys. Therefore, an external force acts on the pulleys so as to cause the rotational axis to incline from the main scanning direction. If an external force of this kind acts on the pulley, then it is difficult to move the supporting member in the sub-scanning direction with respect to the carriage, in order to adjust the position of the pulley. Furthermore, the slidability of the supporting member with respect to the carriage is impaired by the external force described above, and fine adjustment of the position of the pulley is difficult to achieve.
The present disclosure was devised in view of the problems described above, an object thereof being to improve the accuracy of positional adjustment of a pulley provided on a carriage which supports a mirror.